This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study is to find out the highest and safest dose of PS-341 that can be given in people with abnormal kidney function. This study will also find out what happens to PS-341 in the human body. PS-341 is an experimental anti-cancer compound that blocks the normal breakdown of natural body proteins, which may result in reducing cancer growth and spread. Laboratory tests suggest that PS-341 has activity against variety of different cancers. The FDA has recently approved PS-341 for use in patients with multiple myeloma. Approximately half of the patients with multiple myeloma, and about one out of ten of all cancer patients have some degree of abnormal kidney function, which can affect their cancer treatment because some of the drugs are eliminated by the kidney. Currently, there is insufficient information regarding the safety and possible need to adjust doses in patients with abnormal kidney function. Since myeloma patients often have diminished kidney function, it is important to learn about the body's handling of this drug in patients with abnormal kidney function. This trial is designed to obtain information that will assist in selecting the proper dose and timing of this treatment for myeloma patients and for patients with other types of tumors that might be treated with PS-341.